There were more than seven million new cases of the Omicron variant across Europe in the first week of January, the World Health Organization said on Tuesday.
According to Hans Kluge, WHO Europe Director, 26 countries in the region reported that more than 1 per cent of their populations are being infected with Covid each week, The Telegraph reported.
Kluge warned that there is now a "closing window of opportunity" for countries to prevent their health systems from being overwhelmed.
He cited estimates from the Institute of Health Metrics at the University of Washington which projected that half of the population in Western Europe will be infected with Covid in the next six to eight weeks.
"Omicron moves faster and wider than any (previous) variants we have seen," he was quoted as saying at a media briefing.
Kluge also called for countries to mandate the use of masks indoors and to prioritise vaccination, including booster dose of at-risk population, including health workers and elderly people.
Further, he said that as Omicron moves east across the European continent, the variant will take a much higher toll on countries with lower vaccination coverage rates.
Covid hospitalisation rate, in Denmark, was six times higher in people who weren't vaccinated compared to those who had been immunised, Kluge noted.
WHO chief Tedros Adhanom Ghebreyesus had previously pleaded with the rich countries not to offer booster doses and to donate them instead to poorer countries where vulnerable groups are yet to be immunised.
"No country can boost its way out of the pandemic," he said, adding that the current vaccines "remain effective against both the Delta and Omicron variants".